Monoclonal hybridomas have been developed against a number of viruses including Coxsackie B4 Encephalomyocarditis (EMC) and Mengo. These monoclonal antibodies will be used as probes of antigenic variation in laboratory strains of differing tissue tropism as well as of recent clinical isolates. Non-neutralized variants will also be isolated and characterized. Autoimmune antibody producing hybridomas have been developed from splenic leukocytes of reovirus type 1 infected mice.